Low-voltage electric wiring in household installations such as telephone outlets, does not require use of the metal outlet boxes required for the typical 110 volt outlets. Therefore, it is permissible to install low-voltage sockets typically mounted on receptacle plates, similar in appearance to switch plates, directly to the wall material.
One method of mounting which avoids the use of outlet boxes when mounting to board-type wall material, is shown in U.S. Pat. No. 4,576,431; this discloses a subplate for outlet sockets on such receptacle plates. That subplate has bendable horizontal legs extending from its vertical longer edges; these legs are pressed inwardly against the side edges of a wallboard opening and then outward behind the wallboard. The receptacle plate is then fastened by top and bottom screw holes into the wall material through the frame portion of the subplate.